The invention relates to an apparatus for injection moulding of an injection moulded object forming two partial layers from two at least partially overlapping components, in particular a magnetic tape cassette casing in a cavity of an injection moulding mould formed by a fixed mould half (1) and a moving mould half (2) with a moving core (2a) for the two components (3, 4), wherein a projection (5) on one of the mould halves limits one of the partial cavities.
Nowadays, multi-component injection moulding is a process frequently employed for the production of plastics mouldings such as multi-coloured car rear lights, bumpers for motor vehicles or hollow bodies. The different methods employed are described in the publications "Rationalisieren durch Mehrkomponenten-Spritzgiessen" (Journal "Kunststoffe", 78, (1988), pages 665 to 669 and an article about multicoloured injection moulding in the journal 'Plastikverarbeiter" 39, (1988), pages 148-152).
An apparatus with several mould jaws which can be displaced transversely to the tool axis is known from DE-GM 85 02 378, in which a projection on one of the mould jaws penetrates into the cavity and thus provides a separating line for the two components during production thereof. This apparatus can be used for three-dimensional shaped articles such as bumpers, but not for flat shapes such as magnetic tape cassette casings. Furthermore, injection moulding apparatuses are known in which the nozzle-side as well as the ejector-side core are moved in the direction of the tool axis. These apparatuses entail a complicated tool construction for production of magnetic tape cassette casings and do not allow the use of needle shut-off nozzles with direct feed orifice.
EP 0 152 693 describes an apparatus for producing a magnetic tape cassette casing, in which adjacent, transparent and opaque casing parts are produced by successive injection moulding by means of an axially displaceable mould jaw having a notched rim. U.S. Pat. No. 4,726,758 describes a corresponding apparatus for the same purpose, in which a projection in the axially displaceable moving mould half engages in a corresponding recess in the fixed mould half. EP 0 248 106 discloses an injection moulding apparatus for the production of mouldings from three different plastics components, in which a sliding control means controls the supply of the different components.